It has been estimated that over 80% of the electric power used in the United States is obtained from generators driven by steam turbines. These comprise large machines that are rated between 500,000 and 1,000,000 kW and even larger. Many of the steam turbines in service today were built years ago when metallurgical practices were very different than they are today. Thus, older steam turbine rotors were produced from steel made in the open hearth process which has high levels of residual elements compared with steels made today using the basic oxygen process. These residual elements comprise sulfur, oxygen and phosphorous but may include others. The elements can affect the weldability of rotor steel. This has complicated the repair of rotors in older steam turbines.
In some instances, old rotors can be welded successfully by use of basic weld fluxes that aid in the deoxidation and desulfurization of the rotor steel adjacent the weld. Sometimes, however, use of basic fluxes is not sufficient.
It is an advantage, according to this invention, to provide a method of arc welding to build the thickness of high sulfur, low alloy steel such as encountered in the repair of very old steam turbine rotors.